Breathable gas inlet control device for respiratory treatment apparatus

ABSTRACT

A breathable gas inlet control device permits flow regulation at the inlet of a flow generator for a respiratory treatment apparatus such as a ventilator or continuous positive airway pressure device. The device may implement a variable inlet aperture size based on flow conditions. In one embodiment, an inlet flow seal opens or closes the inlet to a blower in accordance with changes in pressure within a seal activation chamber near the seal. The seal may be formed by a flexible membrane. A controller selectively changes the pressure of the seal activation chamber by controlling a set of one or more flow control valves to selectively stop forward flow, prevent back flow or lock open the seal to permit either back flow or forward flow. The controller may set the flow control valves as a function of detected respiratory conditions based on data from pressure and/or flow sensors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Patent Application No. 61/317,483 filed Mar. 25, 2010, thedisclosure of which Is hereby incorporated herein by reference.

FIELD OF THE TECHNOLOGY

The present technology relates to valves for controlling gas flow inrespiratory treatment apparatus. More specifically, it relates to valvesto limit gas flow, such as inlet gas flow, to a flow generator inrespiratory treatment apparatus such as continuous positive airwaypressure treatment devices, ventilator devices or other airflow devicesfor treating respiratory-related conditions.

BACKGROUND OF THE TECHNOLOGY

Respiratory treatment apparatus can function to supply a patient with asupply of clean breathable, gas (usually air, with or withoutsupplemental oxygen) at a therapeutic pressure or pressures, atappropriate times during the subject's breathing cycle. Pressure changesmay be implemented in a synchronized fashion so as to permit greaterpressures during inspiration and lower pressures during expiration.Therapeutic pressure is also known as the ventilation pressure.

Respiratory treatment apparatus typically include a flow generator, anair filter, a mask, an air delivery conduit connecting the flowgenerator to the mask, various sensors and a microprocessor-basedcontroller. Optionally, in lieu of a mask, a tracheotomy tube, may alsoserve as a patient interface. The flow generator may include aservo-controlled motor, volute and an impeller that forms a blower. Insome, cases a brake for the motor may be implemented to more rapidlyreduce the speed of the blower so as to overcome the inertia of themotor and impeller. The braking can permit the blower to more rapidlyachieve a lower pressure condition in time for synchronization withexpiration despite the inertia. In some cases the flow generator mayalso include a valve capable of discharging generated air to atmosphereas a means for altering the pressure delivered to the patient as ahalternative to motor speed control. The sensors measure, amongst otherthings, motor speed, mass flow rate and outlet pressure, such as with apressure transducer or the like. The apparatus may optionally include ahumidifier and/or heater elements in the path of the air deliverycircuit. The controller may include data storage capacity with orwithout integrated data retrieval and display functions.

These devices may be used for the treatment of many conditions, forexample respiratory insufficiency or failure due to lung, neuromuscularor musculoskeletal disease and diseases of respiratory control. They mayalso be used for conditions related to sleep disordered breathing (SDB)(including mild obstructive sleep apnea (OSA)), allergy induced upperairway obstruction or early viral infection of the upper airway.

It may be desirable to develop further methods and devices forcontrolling the flow of breathable gas in a respiratory treatmentapparatus during operations.

SUMMARY OF THE TECHNOLOGY

An aspect of some embodiments of the current technology is to provide aflow control device for a respiratory treatment apparatus.

Another aspect, of some embodiments of the technology is to provide avariable inlet for a respiratory treatment apparatus.

A still further aspect of some embodiments of the technology is toprovide an inlet flow control device that is adjustable in accordancewith patient flow.

A yet further feature of some embodiments of the technology is toprovide a flow control device to prevent back flow.

A still further aspect of some embodiments, of the technology is toprovide such a flow control device to prevent a back flow or return ofbreathable gas in a respiratory treatment apparatus based on detectedconditions.

Another aspect of some embodiments of the technology is to provide aflow control seal for an inlet of a flow generator.

For example, in some embodiments of the technology, a respiratorytreatment apparatus may be configured to provide a flow of breathablegas to a patient. The apparatus may include a gas inlet having avariable aperture that is adjustable between closed and fully open and agas outlet. A flow generator of the apparatus may be adapted to providea supply of pressurized breathable gas from the gas inlet, and to thegas outlet. The apparatus may also include a controller to control, thelevel of pressure generated by the flow generator. The aperture may varyin opening size as a function of a level of flow of breathable gasprovided adjacent to the gas outlet. The variable aperture may include aflexible seal. It may also be configured for proportional opening over arange of flow values where the range of flow is between a first flowvalue and a second flow value. In some embodiments, the first flow valuemay be approximately 0 liters per minute and the second flow value maybe approximately 70 liters per minute. Optionally, the variable aperturemay be configured at a fixed opening size for flow values above therange of flow. The variable aperture may also be configured to be closedat the first. flow value of the range of flow. The variable aperture mayalso include a seal activation chamber. The pressure of the sealactivation chamber may be set by control of one or moreelectro-mechanical valves. The controller may set the electromechanicalvalve as a function of a measure of the level of flow of breathable gas.Optionally, the aperture may include an electro-mechanical valve and thecontroller may be configured to set a size of an opening of theelectromechanical valve as a function of a measure of the level of flowof breathable gas.

In some embodiments of the technology, a respiratory treatment apparatusis configured to provide a supply of pressurized breathable gas to apatient in successive respiratory cycles where each cycle includes aninspiration phase and an expiration phase. The apparatus may include agas inlet, a gas outlet and a flow generator that is adapted to receivean inlet flow of breathable gas from the gas inlet and to pressurize thebreathable, gas prior to delivery to the gas outlet. A controller of theapparatus may then be adapted to control the level of pressure generatedby the flow generator to provide an inspiratory pressure and anexpiratory pressure wherein during at least a portion of the expirationphase the inlet flow to the flow generator is interrupted to facilitatethe reduction, in pressure from the inspiratory pressure to theexpiratory pressure. This interruption of the inlet flow may then unloada blower of the flow generator. In some such embodiments, the controllermay be configured to interrupt the inlet flow by setting one or moreelectro-mechanical valves. For example, the apparatus may include aflexible seal in a flow path of the inlet and a seal activation chamberproximate to the flexible seal. The setting of the electro-mechanicalvalve may then control a pressure level of the seal activation chamber.

In some embodiments of the present technology, a flow generator for arespiratory treatment apparatus includes a motor, a volute and animpeller coupled with the motor. A housing for the impeller has a gasinlet and a gas outlet. The gas outlet is adaptable for a conduit of apatient interface to deliver breathable gas as a respiratory treatment.The apparatus also includes an inlet flow seal positioned to selectivelyopen and close the gas inlet. The inlet flow seal has a first sideinternally proximate to an inlet chamber of the gas inlet and the inletflow seal has a second side, externally proximate to the inlet chamberof the gas inlet. The seal activation chamber is configured proximate tothe second side of the inlet flow seal to permit a negative pressure inthe seal activation chamber to open the gas inlet to a flow ofbreathable gas.

In some embodiments, the housing also includes first and second portsand a pressure communication conduit to connect a posterior portion ofthe inlet chamber and the seal activation chamber for pressurecommunication such that a negative pressure in the inlet chamber resultsin a negative pressure in the seal activation chamber. Optionally, theflow generator may also include a first flow control valve coupled withthe pressure communication conduit. The first flow control valve may beconfigured to selectively switch the seal activation chamber to thepressure in the pressure communication conduit associated with the inletchamber pressure or to atmospheric pressure.

In some embodiments, the negative pressure in the seal activationchamber is due to the flow of breathable gas flowing towards the gasoutlet. Moreover, this flow can be controlled by a breathing cycle.Thus, configuration of the seal activation chamber and the setting ofthe flow control valve may allow flow to a patient from the inletthrough the flow generator and to the outlet.

Optionally, the negative pressure in the seal activation chamber may bediscontinued when the flow control valve is set to open to atmosphericpressure resulting in a substantial ambient pressure equalization in theseal activation chamber. This equalization may then permit closure ofthe gas inlet to a flow of breathable gas such as the flow from theinlet through the flow generator and to the outlet.

Back flow through the gas inlet may also be prevented when the device isset to permit equalization between the seal activation chamber and thegas inlet chamber. The back flow from the gas outlet to the gas inletincreases pressure in the inlet chamber and the seal activation chambersuch that the increase in pressure permits closure of the gas inlet withthe seal.

In still further embodiment a second flow control valve is coupled withthe first flow control valve. The second flow control valve may beconfigured to selectively switch the gas inlet of the first flow controlvalve to pressure of the gas outlet or ambient pressure. The switch toambient pressure may be provided directly to ambient or to the anteriorportion of the inlet chamber which can be substantially equivalent toambient pressure.

In some embodiments, the flow control, device may be selectively set topermit back flow. For example, the. apparatus may set one or morecontrol valves to seal a desired pressure level within the sealactivation chamber such that the seal activation chamber discontinuesequalizing with a pressure of the gas inlet chamber and an ambientpressure. The sealed pressure level therein, which may be a negativepressure, can lock the inlet flow seal in an open position even when thepressure of the inlet chamber increases due to the back flow.

Optionally, a controller of the flow generator may be configured to setthe first flow control valve to permit a negative pressure in the sealactivation chamber to open the gas inlet to a flow of breathable gas inresponse to a detection of a condition of inspiration. The controllermay also be configured to set the first and optionally the second flowcontrol valves to discontinue the negative pressure in the sealactivation chamber to close the gas inlet to a flow of breathable gas inresponse to a detection of a condition of expiration.

The technology may also be implemented as a respiratory treatmentapparatus that includes a flow generator to produce a breathable gas ata pressure above atmospheric pressure for a pressure therapy regime. Theflow generator may include a gas inlet and a gas outlet, where the gasoutlet is adaptable for a conduit of a patient interface to deliver thebreathable gas. The apparatus may also Include a controller to controlthe flow generator to produce the breathable gas according to a pressuretherapy regime. An inlet flow seal of the apparatus may be positioned toselectively open and close the gas inlet where the inlet flow seal has afirst side internally proximate to an inlet chamber of the gas inlet anda second side externally proximate to the inlet chamber of the gasinlet. The apparatus may also include a seal activation chamberproximate to the second side of the inlet flow seal wherein a negativepressure in the seal activation chamber permits opening of the gas inletto a flow of breathable gas.

In some embodiments of the apparatus, a pressure, communication conduitconnects the interior inlet chamber and the seal activation chamber forpressure communication such that a change in pressure in the interiorinlet chamber changes the pressure in the seal activation chamber. Instill further embodiments of the apparatus, a first flow control valveis coupled with the seal activation chamber and is configured toselectively switch between the pressure communication conduit andatmospheric pressure under control of the controller. In some furtherembodiments a second flow control valve of the apparatus may be coupledwith the first control valve and be configured to selectively switchbetween (a) equalizing pressure (permitting flow) between the gas inletand the gas outlet and (b) equalizing pressure (permitting flow) betweenthe gas inlet and the first control valve. In such a case, the pressureat the gas inlet may be substantially ambient pressure.

The flow generator of the apparatus may include a motor, volute and animpeller configured between the gas inlet and the gas outlet. Similar topreviously described embodiments, one or more of the valves may be setto control the pressure in the chamber and the seal so as to permitflow, stop flow, prevent back flow and permit back flow.

In some embodiments of the technology, a system regulates flow to a flowgenerator in a respiratory treatment apparatus. The system may include agas inlet to a flow generator through which a flow of breathable gas isdrawn. The system may also include means for sealing off the flow at thegas inlet. The means for sealing may have a first side internallyproximate to an inlet chamber of the gas inlet and a second sideexternally proximate to the inlet chamber of the gas inlet. The systemmay also include a chamber means that is proximate to the second side ofthe means for sealing wherein a negative pressure therein opens the gasinlet at the means for sealing. The system may also include a means forchanging pressure to the chamber means in accordance with a change inpressure in the gas inlet. Still further, the system may include meansfor selectively discontinuing the change in pressure in the chambermeans while permitting the change in pressure in the gas inlet.

Optionally, the aforementioned embodiments may also include an oxygeninput port coupled to the inlet to inject oxygen gas into the gas inlet.

Additional features of the present respiratory treatment apparatustechnology will, be apparent from a review of the following detaileddiscussion, drawings and claims.

BRIEF DESCRIPTION OF DRAWINGS

The present technology is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings, in whichlike reference numerals refer to similar elements including:

FIG. 1 is a schematic diagram illustrating components of an inletcontrol device for a flow generator in an embodiment of the presenttechnology;

FIG. 1-A is a diagram illustration an area ratio between a seal and aninlet aperture in an example embodiment of the technology;

FIG. 2 is a schematic diagram illustrating, pressurized operation of thecomponents of FIG. 1;

FIG. 3 is a schematic diagram illustrating de-pressurized operation ofthe components of/FIG. 1;

FIG. 3-A is a schematic diagram illustrating a blocked-flow operation ofthe components of FIG. 1;

FIG. 3-B is a schematic diagram illustrating a patient back flowoperation of the components of FIG. 1;

FIG. 4 is an illustration of example inlet control components for anassembly of the present technology;

FIG. 5 is a side view cross-sectional illustration of example inletcontrol components of FIG. 4 installed on a volute housing of a blowerin an embodiment of the present technology;

FIG. 5-A is a side view exploded perspective of inlet control componentsfor another embodiment the present technology;

FIG. 6 is an illustration of example components of a respiratorytreatment apparatus with an inlet controller of the technology;

FIG. 7 is a schematic diagram illustrating components of an inletcontrol device for a flow generator in a further respiratory treatmentapparatus embodiment of the technology;

FIG. 8 is a schematic diagram illustrating operation of the componentsof the embodiment of FIG. 7 in an initial inspiration state;

FIG. 9 is a schematic diagram illustrating operation of the componentsof the embodiment of FIG. 7 in a maximum inspiratory flow state;

FIG. 10 is a schematic diagram illustrating operation of the componentsof the embodiment of FIG. 7 in an expiratory state;

FIG. 11 is a schematic diagram illustrating operation of the componentsof the embodiment of FIG. 7 in an inspiratory state for a non-ventedrespiratory treatment apparatus;

FIG. 12 is a schematic diagram illustrating operation of the componentsof the embodiment of FIG. 7 in an initial expiratory state, for anon-vented respiratory treatment apparatus;

FIG. 13 is a schematic diagram illustrating operation of the componentsof the embodiment of FIG. 7 in an expiratory state for a non-ventedrespiratory treatment apparatus; and

FIG. 14 is a schematic diagram illustrating operation of the componentsof the embodiment of FIG. 7 in an inspiratory pause state for anon-vented respiratory treatment apparatus; and

FIG. 15 is a schematic diagram illustrating operation of the componentsof the embodiment of FIG. 7 in a failure state for a non-ventedrespiratory treatment apparatus.

DETAILED DESCRIPTION

Example embodiments of the current technology may be implemented with abreathable gas inlet control device 102 for a flow generator or arespiratory treatment apparatus including components illustrated in theschematic diagram of FIG. 1. Typically, the flow generator, such as aservo-controller blower 104, will include a motor, volute and impeller105. With the impeller 105, the blower can produce a flow of breathablegas (e.g., air) to the gas outlet 106. Although FIG. 1 illustrates aflow generator of the blower type, also known as a radial compressor,other flow generators may be utilized such as a piston based compressor.In a respiratory treatment apparatus, the gas outlet 106 will typicallybe configured for coupling with a patient interface for respiratorytreatment such as a delivery or supply conduit and mask or tracheotomytube (not shown).

The breathable gas can be drawn into the blower through a gas inlet 108by powered rotation of the impeller. Rotation of the impeller 105creates a lower gas pressure condition at the inlet and a higher gaspressure condition at the outlet relative to ambient or atmosphericpressure. The gas inlet can be formed by an inlet chamber 110 thatserves as a path that directs, a flow of gas drawn into, the impeller105. As shown in FIG. 1, an aperture 112 of the inlet chamber 110 may besealed by an inlet flow seal 114. Controlled movement of the inlet flowseal 114 serves to impede flow by preventing or permitting gas transferbetween an anterior portion 110A of the gas inlet chamber 110 exteriorof the seal and a posterior portion 110P of the gas inlet 108 interiorof the seal.

As illustrated, in FIG. 1, the inlet flow seal 114 is coupled to acavity or seal activation chamber 116. Selective control of the gaspressure within the seal activation chamber serves to control themovement of the inlet flow seal 114. For example, the inlet flow seal114 may be formed by a flexible membrane. The membrane may be formed andpositioned to permit it to resiliently close or seal the aperture 112under a normal pressure condition such as when an ambient pressurecondition exists within the seal activation chamber 114 and in the gasinlet 108. As illustrated in the embodiment of FIG. 1, such a pressurecondition may exist when the blower 104 is not operating. Moreover,depending on the resilience of the seal and/or the pressure condition inthe seal activation chamber, the seal can prevent a back flow of gasfrom the posterior portion 110P of the inlet chamber 110 toward theanterior portion 110A of the Inlet chamber 110. Thus, the inlet, flowseal may also operate as a non-return valve.

The cross-sectional area of the inlet flow seal 114 (i.e., the surfacearea of the seal) may be designed to be larger than the cress-sectionalarea of the gas passageway of the inlet aperture 112 as illustrated inFIG. 1-A. Consequently, the cross-sectional area ratio of the apertureto the inlet flow seal can be greater than 1:1, preferably between about1:1.5 and about 1:3, more, preferably the ratio is about 1:2. In theexample of FIG. 1-A, the surface area 115 of the seal 114 is about twotimes the cross-sectional area 113 of the gas passageway 112 of theinlet aperture (i.e., area ratio AR₂/AR₁=½).

In the embodiment of FIG. 1, a flow control valve 118, such as anelectro-mechanical valve (e.g., a three port, two way valve), may beimplemented to permit changes to the pressurization of the sealactivation chamber 116. For example, as illustrated, the flow controlvalve 118 may be selectively set to permit the pressure of the, sealactivation chamber 116 to equalize with different pressures such as withan ambient pressure (illustrated in FIG. 1 as arrow “AP”) through afirst conduit 120 or another pressure of the inlet chamber 110 through asecond conduit or the pressure communication conduit 122, such as theambient pressure of the posterior portion 110P of the inlet chamber 110when the blower is not operating.

Several operational modes of the apparatus of FIG. 1 will now bedescribed with reference to FIGS. 2, 3, 3-A and 3-B.

As illustrated in FIG. 2, a negative or decreased pressure relative toambient pressure may exist within the posterior portion 110P of theinlet chamber 110. This negative pressure (illustrated in FIG. 2 asarrow “DP”) may be communicated to the seal activation chamber 116 viathe pressure communication conduit 122 by operation of the flow controlvalve 118. For example, as further illustrated in FIG. 2, when theblower is activated and the flow is directed towards the gas outlet 106,the flow control valve 118 may be set to permit pressurization of theseal activation chamber 116 at the negative pressure “DP” of the inletchamber 110 caused by the pressure of the inwards flow of breathable gassuch as when the patient inhales (i.e., inspiration). The pressure maybe communicated to the seal activation chamber 116 through the pressurecommunication conduit 122 serving as a pneumatic link. Significantly,the seal activation chamber 116 and the inlet flow seal 114 may beconfigured to permit opening of the aperture 112 as a result of thischange in pressure in the seal activation chamber 116. In this regard,the rotation of the impeller of the blower acts as a pressure source butthe pressure drop in the posterior portion 110P of the inlet chamber 110relative to the anterior portion 110A that opens the seal is aconsequence of flow through the inlet chamber 110 rather than simplyfrom the rotation of the impeller. For example, the flow through theposterior portion 110P may be controlled of induced by the breathingcycle of the patient whether or not the blower is powered. Moreover, asillustrated in more detail herein, in some states of the apparatus theblower may be powered (e.g., rotating) but there may be no flow through,the posterior portion 110P, such as when the output of the blower isblocked. Nevertheless, if patient flow exists, the impeller-inducedpressure in conjunction with the patient's flow-induced pressure mayboth contribute to the level of pressure, that will exist in theposterior portion.

The size of the aperture 112 and the seal 114 as well as the flexibilityof the seal can be chosen so that the decrease in pressure within thechamber retracts one or more portions of the seal into the sealactivation chamber 116. This retraction may withdraw the seal 114 intothe seal activation chamber 116 providing a gap between the anteriorportion 110A of the inlet chamber 110 and the posterior portion 110B ofthe inlet chamber 110. This retraction of the seal will then permit gasflow between the seal and the aperture from the anterior portion 110A tothe posterior portion 110P and then into the impeller.

Depending on the flexibility of the seal, the extent of the movement ofthe seal can be a function of the varying flow generated by the patient.Thus, the size of the opening formed by the aperture and the flexibleseal during blower operation can be proportional to the induced flow asillustrated by the dotted lines in FIG. 2. For example, greater inwardsflow in the posterior portion 110P of the inlet chamber can result ingreater openings of the aperture 112 to allow more flow into the blower.Similarly, smaller inwards flow in the posterior portion 110P of theinlet chamber can result in smaller openings of the aperture 112 toallow less flow into the blower. The proportional opening permits theforming of a minimum necessary opening size sufficient to permit thedesired flow drawn by the blower. Since larger openings can causegreater noise as the flow of gas passes across the opening, a potentialbenefit of such a proportional flow opening is a reduction of noise.Such a feature can be significant for a respiratory treatment apparatusdesigned for treatment of patients during sleep.

Thus, in some embodiments, the inlet control device may be implementedwith a variable inlet opening to a How different levels of flow to besupplied during inspiration as required by the patient. Duringinspiration the seal acts as a passive proportional valve that adjustsits distance from a rim of the aperture 112 to implement a variableopening. The size of the opening then may be related to the level, ofpatient flow. In a particular example embodiment, a simple passivepneumatic (flow) servo control may be implemented as follows:

(a) at 0 flow, the valve is fully closed;

(b) at between approximately >0 and <70 L/min forward flow, the valveaperture size is linked to the flow;

(c) at approximately >70 L/min, the valve is fully opened with a fixed,aperture size.

However, other flow ranges may be configured. When compared to devicesthat have fixed inlet openings, such a variable opening can optimize theworking conditions of the blower and/or decrease the noise radiatingfrom the system.

As further illustrated in FIG. 3, when the blower is activated, the flowcontrol valve 118 may be set to relieve or discontinue thepressurization of the seal activation chamber 116 without necessarilyalso stopping or reducing the powered impeller rotation. For example,the flow control valve 118 may be set to communicate an ambient pressureto the seal activation chamber 116 through the first conduit 120 orpneumatic link. The resultant equalization in pressure in the sealactivation chamber 116 can permit the inlet flow seal 114 to return toits normal configuration adjacent to the aperture 112 and thereby toseal the aperture 112. Moreover, in addition to the seal resilience, inthe event that the blower is still operating (i.e., the impeller isstill rotating) or the patient still inspiring as shown in FIG. 3, thedecreased pressure condition in the posterior portion 110P of the inletchamber 110 in relation to the higher ambient pressure condition ineither of the anterior portion 110A of the inlet chamber 110 or the sealactivation chamber 116 can further serve as a suction force to furtherenforce closing of the seal to the aperture 112.

Accordingly, the seal then can serve as an efficient and rapid means toprevent a flow of gas into the blower (i.e., shut off the inlet supply)without necessarily changing the speed of the blower or necessarilyrelying on braking of the motor of the blower. Avoidance of braking canreduce heat and keep the blower cooler. Avoidance or reduction ofbraking may also serve to reduce energy requirements of the system sinceless current may be required to operate the valves of the inlet flowcontrol device when compared to supplying the current to the flowgenerator to control a reduction in blower speed.

Accordingly, in some example embodiments, the inlet control can beimplemented to reduce pressures delivered by the blower duringexpiration with or without braking of the motor speed. It may also beimplemented to more immediately stop and start generating flow from theblower. For example, a rapid stopping and starting of flow can becontrolled by a controller using this device to then induce a percussivemode of breathing in a patient that may be suitable for causingsecretion removal (e.g., inducing patient coughing).

Thus, the closing of the inlet control device 102 may serve as part of acontrol scheme for making controlled adjustments of the suppliedtreatment gas. For example, this reduction in size of the inlet aperture(e.g., closing) may be implemented to transition from an inspirationpressure to an expiration pressure without relying on a rapiddeceleration of the blower. In this regard, the blower is unloaded byshutting off the flow (e.g., closing of the inlet control device 102).This means that the blower will decelerate more quickly and will notrequire the high levels of induced current normally required whenbraking a blower that is still receiving flow through the inlet. Inother words, the blower does not have any load when it cannot draw airin through the inlet. Thus, the flow can be interrupted with a rapidresponse time due to this unloading of the blower. The ability torapidly control the flow allows the shape of the respiratory treatmentwaveform produced by the flow generator to be more finely tuned. If asharp pressure waveform/response is required then the inlet controldevice aperture can be closed rapidly.

In some other types of devices lacking the present technology, thetransition from inspiration, to expiration can result in a flow spike atthe beginning of expiration due to the time that is required for theblower to slow down. This flow spike can be avoided in embodiments ofthe present technology by the closing of the inlet control device andthereby shutting off inlet flow.

Thus, in some embodiments, the controller may detect an expiratoryrelated condition (e.g., beginning of expiration, end of inspiration,etc.) from the sensors (e.g., a measure from a flow sensor) and set thevalves of the inlet control device to close the inlet aperture andthereby interrupt flow to the flow generator. Optionally, the controllermay also simultaneously or contemporaneously change a setting (e.g.,reduce current) of the flow generator to, for example, reduce a speed ofthe flow generator to a setting suitable for generating a pressureappropriate for expiration (e.g., an expiratory pressure level). Such acontroller change might also involve the setting of a flow generatorused for generating a positive end expiratory pressure level (PEEP).Thus, the control of the inlet flow device, and optionally the flowgenerator, can also assist in implementing a desired shape of agenerated respiratory treatment pressure waveform.

As illustrated, in FIG. 3-A, the blower may be activated while the flowcontrol valve 118 may be set to equalize the pressure of the sealactivation chamber 116 and the posterior portion 110P of the inletchamber 110. Moreover, the output of the blower at or beyond the outlet106 may be blocked (e.g., due to some problem of the patient interfaceor if the patient is neither inhaling nor exhaling) so as to preventblower induced flow out of the outlet 106. During this operation,without patient flow, the seal 114 can remain in a position to close theaperture 112 due to the configuration of the seal and the equalizedpressure of the seal activation chamber 116 and the posterior portion110P of the inlet chamber 110, which will be approximately the samepressure as the anterior portion 110 of the inlet chamber 110.

Shutting off the flow also results in other benefits such as when it isimplemented to prevent back flow with a non-vented mask system. Forexample, as illustrated in FIG. 3-B, the blower may be activated whilethe flow control valve 118 may be set to equalize the pressure of theseal activation chamber 116 and the posterior, portion 110P of the inletchamber 110. In such a condition, a patient might expire so as to inducea back flow BF condition into the outlet 106 and thereby create apositive pressure (shown as “HP” in FIG. 3-B), relative to ambient, inthe posterior portion 110P of the inlet chamber 110. However, in such acase, the seal 114 can remain in a position to close the aperture 112and prevent the back flow due to the configuration of the seal and theequalized pressure of the seal activation chamber 116 and the posteriorportion 110P of the inlet chamber 110, even though the positive pressureHP of the posterior portion 110P would exceed the ambient pressure inthe anterior portion 110A of the inlet chamber 110.

The prevention of back flow can also have benefits for a system thatutilizes oxygen. For example, when oxygen is injected after ordownstream of the blower as discussed in more detail herein, shuttingoff the flow during expiration by closing the valve means that theoxygen may be maintained in the pressure side of the device (e.g., nooxygen escapes outside the device). Also this arrangement may reduce theexposure of the motor to oxygen as there is no or minimal oxygenbackflow through the blower.

Components of an example inlet control assembly are illustrated in FIG.4. The inlet flow seal 114 is formed of a flexible material with asealing surface 442. The sealing surface 442 serves as a membrane forplying against, an inlet aperture (not shown) as previously described. Aclamp ring 444 having flexible prongs 446 is configured for clamping theouter perimeter lip 447 of the inlet flow seal 114 to a chamber body 448to form the seal activation chamber 116 between the chamber body and theinlet flow seal. The chamber body 448 includes holes 450 to permit inletairflow through the chamber body 448 around and externally of the sealactivation chamber 116. Some of the holes may also be spaced and sizedto receive the flexible prongs 446 of the clamp ring 444 when the prongsare snapped or engaged with the holes. The chamber body 448 includes apressure port 452 for communicating the selected pressure from one ormore flow control valves 118 (not shown in FIG. 4).

FIG. 5 contains a cross sectional illustration of the example inletcontrol assembly components coupled to a blower 104 or flow generator.The illustrated blower 104 includes the motor 550 and impeller 105coupled to a volute 552 that serves as a housing for the impeller 105 ofthe flow generator. In this embodiment, the volute includes the flowinlet 108. When installed, the sealing surface 442 of the inlet flowseal 114 plies against the circumference of a rim of the flow inlet 108.During the operations previously discussed, the rim of the inlet 108 andthe retraction of the sealing surface 442 forms an opening at theaperture 112. In this embodiment, the wall of the volute that serves asthe inlet 108 includes a pressure port 554. The pressure port 554 of theinlet 108 permits an exchange of pressure between the posterior portionof the inlet chamber 110P and the seal activation chamber 116 through aconduit (not shown in FIG. 5) and the flow control valve 118 (also notshown in FIG. 5).

As illustrated in FIG. 5, the particular structure of this embodimentmay have the potential for miniaturization. That is, its compact designcan reduce the size of the housing of a respiratory treatment apparatus.In this regard, the location of the seal and seal activation chamber atthe inlet and close to the blower can provide a reduction in space. Inthis regard, portions of the components of the inlet control device maybe integrated with a volute for the blower. However, it is also possiblein alternative embodiments to locate, the seal activation chamber, andseal elsewhere with respect to the apparatus or blower. For example, itmay be attachable and/or removable to the blower or blower housing via atube or other conduit (not shown).

Another embodiment of the inlet control assembly is illustrated in FIG.5-A. In this embodiment, the inlet flow seal 114 is clamped betweenmounting ring 555 and chamber body 448. The mounting ring 555 is adaptedfor removable installation with the wall of the inlet chamber 110. Forexample, side clips or threads (not shown) of the mounting ring 555 maymate with receiving grooves (not shown) of the wall of the inlet chamber110. When snapped or rotated in place, the mounting ring secures theinlet control assembly to the blower volute 552. In this example of theinlet control assembly, the mounting ring 555 includes flexible prongs446 configured for clamping the outer perimeter lip 447 of the inletflow seal 114 to the chamber body 448 to form the seal activationchamber 116 between the chamber body and the inlet flow seal. Thechamber body 448 includes holes 450 to permit inlet airflow through thechamber body 448 around and externally of the seal activation chamber116. Some of the holes may also be spaced and sized to receive theflexible prongs 446 of the mounting ring 555 when the prongs are snappedor engaged with the holes. The chamber body 448 includes . the pressureport 452 for communicating the selected pressure from one or more flowcontrol valves 118 (not shown in FIG. 4). Another pressure port 554leading to the posterior portion 110P of the inlet chamber 110 isintegrated into the volute at the wall of the inlet chamber.

In the embodiments, of FIGS. 5 and 5A various arrangements are shown forcoupling components of the inlet control to the housing of a blower orthe inlet of a blower. However, additional configurations may also beimplemented to achieve a connection with a blower. For example, some orall of the inlet control components may be configured as a removableunit or module. The unit or module may then be removably coupled to aportion of an inlet of a blower or housing thereof. For example, theunit or module may be configured with a bayonet connection or a bayonetcoupler. Similarly, the unit, or module may be coupled to the inlet of ablower such that it mates with the inlet of the blower by aninterference fit. Other coupling arrangements may also be implementedsuch as a snap-fit arrangement.

Example Respiratory Treatment Apparatus Operation

As previously discussed, the breathable gas inlet control 102 device maybe implemented, with the flow generator of a respiratory treatmentapparatus 600, such as the ventilator or continuous positive airwaypressure device illustrated in FIG. 6. Such an apparatus includes acontroller 664, with one or more microcontrollers or processors, so thatthe respiratory treatment apparatus 600 may be configured with one moretreatment regimes for setting the pressure delivered by the pressuregenerator or blower in conjunction with signals from optional pressuresensors(s) and/or flow sensor(s). Thus, the controller may adjust thespeed of the blower during patient treatment to treat detectedconditions (e.g., flow limitation, inadequate ventilation, apnea, etc.)and/or synchronize pressure changes during detected patient respirationto simulate or support respiration. In addition, the controller 664 maybe configured to selectively set the pressure of the seal activationchamber 116 by control of one or more flow control valves 118 andthereby serve as an inlet flow controller 666 for permitting flow ofgas. (e.g., air or oxygen and air) to the blower and/or to prevent aback flow of gas from the blower. In this manner, the inlet flowcontroller 666 controls the inlet flow seal 114.

Thus, the controller 664 or inlet flow controller 666 will typicallyinclude one or more processors configured to implement particularcontrol methodologies such as the algorithms described in more detailherein. To this end, the controller may include integrated chips, amemory and/or other control instruction, data or information storagemedium. For example, programmed instructions encompassing such a controlmethodology may be coded on integrated chips in the memory of thedevice. Such instructions may also or alternatively be loaded assoftware or firmware using an appropriate data storage medium. Thecontroller will also typically include a bus or electronic interface forsetting the flow control valves as well as the other components of theapparatus (e.g., blower motor).

During operation of the respiratory treatment apparatus and depending onthe desired usage, the inlet flow controller 666 may set the gas inletcontrol device 102 based on the detection of different conditions of thesystem. For example, from an analysis of pressure and flow data, thecontroller may set the gas control device 102 based on the detection ofdifferent states of the patient's respiratory cycle or enforcing thosestates such as inspiration, expiration, start of inspiration, start ofexpiration, inspiratory peak flow, inspiratory pause, etc. Known methodsfor the detection of these conditions from pressure and/or flow data orfor enforcing them (e.g. timed backup breathing rates) may beimplemented by the programming or the circuits; of the controller.Various examples of the setting of the gas inlet control device 102 by acontroller in different system configurations and respiratory states areillustrated in FIGS. 7 through 15.

In the respiratory apparatus configuration of FIGS. 7 through 15 anadditional flow control valve 772 (or pressure relief valve) is addedunder the control of the inlet flow controller 666. The additional flowcontrol valve 772 selectively permits (a) an equalization of pressure orflow between the outlet 106 of the blower 104 and the anterior portion110A of the inlet chamber 110 through back flow conduit 779 or (b) anequalization of pressure or flow between first conduit 120 to the firstcontrol valve 118 and the anterior portion 110A of the inlet chamber110. However, in some embodiments, the optional back flow conduit 779may not be present. In such a case, the port of the flow control valve772 for the optional back flow conduit 779 may be capped such that theflow control valve 772 serves only as a 2-way valve able to selectivelyconduct gas between the inlet 108 and the first conduit 120. Optionally,the flow control valve 772 may be replaced by a 2-way valve.

In the example of FIG. 7, the flow control valve 772 can be implementedwith a normal state that permits equalization of pressure or permitsflow between the outlet 106 of the blower 104 and the anterior portion110A of the inlet chamber 110. Such a recirculation of flow from theoutlet of the blower 106 to the anterior portion 110A of the inletchamber 110 may assist with cooling of the motor and may provide bettercontrol of the valve at low flows. Upon activation by the controller666, the flow control valve 772 may then be switched to equalizepressure or permit flow between first control valve 118 via firstconduit 120 and the anterior portion 110A of the inlet chamber 110.Similarly, the flow control valve 118 may be implemented with a normalstate that permits equalization of pressure or permits flow between theposterior portion 110P of the inlet chamber 110 and the seal activationchamber 116. Upon activation by the controller 666, the flow controlvalve 118 may then be switched to equalize pressure or permit flowbetween the first conduit 120 and the seal activation chamber 116. Inthis case, the pressure of the seal activation chamber 116 is furtherdependent on the setting of the flow control valve 772. For example,when the flow control valve 118 is in its activated state and the flowcontrol, valve 772 is in its normal state, the seal activation chamber116 will effectively be sealed at the last pressure previously applied.Such a case may permit the seal activation chamber 116 to “lock” theinlet flow seal 114 open if a negative pressure condition existed in theseal activation chamber 116 prior to the activation of the flow controlvalve 118. In such a case, the inlet flow seal may be open even upondeactivation of the blower.

Additionally, in the example system of FIGS. 1 through 15, a secondblower or positive end expiratory pressure (PEEP) blower 704 may also beincluded to deliver a positive pressure at the end of patientexpiration. Although it is illustrated, the full operations of the PEEPblower 704 are beyond the scope of the explanation of the gas inletcontrol device 102 of the present technology. Also shown in the diagramis a safety valve 770 in a muffler chamber 777. Generally, the safetyvalve will be open during patient inspiration and closed during patientexpiration.

Operations will now be described with reference to FIGS. 8 to 10.Generally, FIGS. 8 to 10 illustrate operations for vented ventilation(i.e., use of the apparatus with a vented patient interface or mask) tothe extent that these figures may show an active or powered controller(i.e., turned on). FIG. 7 is a block diagram illustrating the defaultsetting of the gas inlet control device 102 when the respiratorytreatment apparatus is off the default setting shown in FIG. 7 is thesame whether a vented or non-vented mask is utilized. In this state theflow control valve 772 and flow control valve 118 are not active (i.e.,they are in their normal states).

FIG. 7 also illustrates the settings of the gas inlet control device 102when the controller 664 implements a ventilation pause such as when thecontroller detects that the patient's expiration is complete andinspiration has not yet started. Thus, there is no or very low flow. Thecontroller 664 does not activate either flow control valve 772 or flowcontrol valve 118. While the blower may or may not be powered and it maybe rotating in either case, the gas inlet control device 102 could beclosed so as to prevent back flow from the blower to the anteriorportion 110A of the inlet chamber 110.

FIG. 8 is a block diagram illustrating the setting of the gas inletcontrol device 102 when the respiratory treatment apparatus is on andthe controller 664 implements the start of inspiration by eitherdetection of patient inspiration or initiation of a timed backup. Thecontroller 664 does not activate either flow control valve 772 or flowcontrol valve 118. Since in this condition the blower would be poweredto deliver an inspiratory positive airway pressure (IPAP), the patient'shigh inspiratory flow would generate a negative pressure condition orsuction in the posterior portion 110P of the inlet chamber and the sealactivation, chamber 116. Thus, the gas inlet control device 102 would beopen to permit flow to the blower. Additionally, in this configuration,the flow from the outlet 106 through the back flow conduit 779 to theinlet chamber can serve a cooling function. With the leak flow createdwith the back flow conduit, the blower may run at a higher speed. Byallowing greater flow through the blower it can serve to cool theblower.

FIG. 9 is a block diagram illustrating the setting of the gas inletcontrol device 102 when the respiratory treatment apparatus is on andthe controller 664 detects the expected peak flow of patientinspiration. The controller 664 does not activate flow control valve 772but does activate flow control valve 118. In this condition the blowerwould be powered to deliver an inspiratory positive airway pressure(IPAP). The generated negative pressure condition in the posteriorportion 110P of the inlet chamber would then be maintained or sealed inthe seal activation chamber 116 due to the activation of flow controlvalve 118. Thus, the gas inlet control device 102 would be “locked” openor at least partially open (depending on the amount of patient flow atthe time of the activation of flow control valve 118) still permittingflow to the blower.

FIG. 10 is a block diagram illustrating the setting of the gas inletcontrol device 102 when the respiratory treatment apparatus is on andthe controller 664 detects patient expiration after the aboveinspiration. The controller 664 does not activate flow control valve 772but does continue to activate flow control valve 118. In this, conditionthe blower would be powered to deliver an expiratory positive airwaypressure (EPAP). Since the previously generated negative pressurecondition is maintained or sealed in the seal activation chamber 116,the gas inlet control device 102 would be “locked” open or partiallyopen. This would permit back flow from the outlet 106 through the blowerand back out the inlet 108 to permit the patient's expiration flow to bevented through the respiratory treatment apparatus.

FIGS. 11 to 15 illustrate operations for non-vented ventilation (i.e.,use of the apparatus with a non-vented patient interface or mask). Inthis regard, FIG. 11 is a block diagram illustrating the setting of thegas inlet control device 102 when the respiratory treatment apparatus ison and the controller 664 implements the start of inspiration by eitherdetection of patient, inspiration or initiation of a timed backup. Thecontroller 664 does not activate either flow control valve 772 or flowcontrol valve 118. Since in this condition the blower would be poweredto deliver a flow or pressure based on a set point of a closed loopcontrol as a result of the patient's inspiratory flow, there would begenerated a negative pressure condition in the posterior portion 110P ofthe inlet chamber and the seal activation chamber 116. Thus, the gasinlet control device 102 would be open to permit flow to the blower.Additionally, In this configuration, the flow from the outlet 106through the back flow conduit 779 to the inlet chamber can serve acooling function.

FIG. 12 is a block diagram illustrating the setting of the gas inletcontrol device 102 when the respiratory treatment apparatus is on andthe controller 664 detects the start of patient expiration (e.g., bydetecting a peak flow threshold). The controller 664 activates both flowcontrol valve 772 and flow control valve 118. In this condition thecontroller may de-power the blower. Since the seal activation chamber116 has an ambient condition of the anterior portion 110A of the inletchamber 110 as a result of the flow path through both flow control valve772 and flow control valve 118, the gas inlet control device 102 wouldbe closed. The closing of the inlet flow seal and stopping of any inletflow would then tend to slow the natural inertia of the impeller of thede-powered blower like a brake.

FIG. 13 is a block diagram illustrating the setting of the gas inletcontrol device 102 when the respiratory treatment apparatus is on andthe controller 664 detects expiration. Flow-by control may beimplemented. Flow-by control, is control of the seal during expirationto allow a very low level of flow through the inlet to compensate forleak (e.g., 1-2 litres) at the patient interface. The controller 664does not activate either flow control valve 772 or flow control valve118. In this condition the controller may minimally power the blower forgenerating a low level of flow based on a flow set point of a flowcontrol loop. Since the seal activation chamber 116 has a negativepressure condition from the posterior portion 110P of the inlet chamber110 as a result, of the flow path through the flow control valve 118,the gas inlet control device 102 would be partially open. The partialopening of the inlet flow seal would then permit a low flow ofbreathable gas through the blower to the outlet 106.

FIG. 14 is a block diagram illustrating the setting of the gas inletcontrol device 102 when the respiratory treatment apparatus is on andthe controller 664 detects an inspiratory pause or plateau. It may alsobe implemented for an automated positive end expiratory pressure (PEEP)measurement mode. The controller 664 activates, flow control valve 772but does not activate flow control valve 118. In this condition theblower would be powered at a minimum speed. Due to the absence ofpatient flow, the gas inlet control device 102 would be closed.Moreover, the flow back conduit 779 would also be closed as a result ofthe setting of the flow control valve 772. Thus, flow back into therespiratory treatment apparatus from the patient interface or mask wouldbe prevented.

FIG. 15 is a block diagram illustrating the setting of the gas inletcontrol device 102 for a failure mode when the respiratory treatmentapparatus is or and the controller 664 detects that the expiratory valveassociated with the venting of the patient interface or mask is blocked,preventing patient exhalation during expiration. Upon detection of thiscondition, the controller 664 activates both flow control valve 772 andflow control valve 118. In this condition, equalization of pressure ofthe seal activation chamber 116 and the anterior portion 110A of theinlet chamber 110 is permitted. The blower would also be powered to aminimum speed. The patient's expiratory flow would then be sufficient toforce open the inlet flow seal 114 as a result of the positive pressurecreated in the posterior portion 110P of the inlet chamber 110. Thus,the gas inlet control device 102 would be opened. Thus, flow back intothe respiratory treatment apparatus from the patient interface or maskwould be permitted.

In some embodiments, a supply of oxygen may also be mixed with the airsupply to form the mixed breathable gas at the outlet. The oxygen may beinjected in the flow path either downstream or upstream of the blower.For example, in some embodiments, the oxygen may be supplied or injectedinto the flow path at the outlet 106 as indicated by oxygen supply oroxygen inlet port 780 in FIGS. 7-15. For example, a high flow valve maybe implemented to inject the oxygen. Injecting the oxygen after theblower and the valve also assists in preventing the oxygen from escapingback through the system and to atmosphere. This may reduce wastage ofoxygen. Furthermore, injecting the oxygen after the blower prevents orlimits the exposure of the blower and motor to the flammable oxygen,making the device safer. In alternative versions of the apparatus, theoxygen may be inserted or injected into the inlet 108 or inlet chamber110. This may optionally be injected either in the anterior portion 110Aor posterior portion 110P. Thus, the ambient air and oxygen mix wouldthen flow through the blower and be pressurized by the blower at theoutlet 106. This may be implemented by including a gas input port in thewall of the inlet 110. This option is illustrated, in FIGS. 7-15 asalternative oxygen supply or oxygen inlet port 780A. The oxygen may thenbe regulated with a valve at the gas input port. For example, the valvemay regulate a low flow of oxygen with the ambient air. The apparatusmay include oxygen port 780 near the outlet or oxygen 780A near theinlet, or both oxygen ports 780 and 780A to allow a choice of whichoxygen port to use. However, generally in use only one of oxygen ports780 or 780A are utilized.

In the foregoing description and in the accompanying drawings, specificterminology, equations and drawing symbols are set forth to provide athorough understanding of the present technology. In some instances, theterminology and symbols may imply specific details that are not requiredto practice the technology. Moreover, although the technology herein hasbeen described with reference to particular embodiments, it is to beunderstood that these embodiments are merely illustrative of theprinciples and applications of the technology. It is therefore to beunderstood that numerous modifications may be made to the illustrativeembodiments and that other arrangements may be devised without departingfrom the spirit and scope of the technology.

For example, as an alternative to the variable opening provided by theflexible seal as herein discussed, other components may be implementedas a variable opening and may also serve to reduce the level of noiseradiated from the system. In this regard, some embodiments of thetechnology may implement an electrically controlled or electro-magneticcontrol system to vary the size of an opening at the inlet. Such acontrol system (e.g., a processor, a sensor and an electro-magneticvalve coupled together for signaling purposes) that measures flow andlinks or associates the required inspiratory flow to control signals forsetting of the opening/closing size of a valve with variable sizes maybe implemented. Thus, in such an embodiment, the inlet supply of gas tothe blower would traverse through the valve and the aperture of thevalve through which the gas traverses would have various sizes, that maybe mechanically set/controlled. Optionally, the valve of such analternative variable inlet control system may be implemented with asolenoid valve, mechanically controlled disk or mechanical controlledplunger that may move to form the variable opening. Advantageously insuch embodiments the opening and closing of the valve may also becontrolled/sized during expiration to provide a proportionallycontrolled non-return valve to more accurately control the shape of therespiratory waveform. For example, upon detecting a condition ofexpiration by a controller of the valve, the opening size of the valvemay be set as a function of the detected expiratory flow. Such a systemmay be more expensive and may take up more space within a respiratorytreatment apparatus when compared to the flexible seal versionpreviously described.

1. A respiratory treatment apparatus configured to provide a flow ofbreathable gas to a patient, comprising: a gas inlet having a variableaperture that is adjustable between closed and fully open; a gas outlet;and a flow generator adapted to provide a supply of pressurizedbreathable gas from the gas inlet and to the gas outlet; and acontroller to control the level of pressure generated by the flowgenerator, wherein the aperture varies in opening size as a function ofa level of flow of breathable gas provided adjacent to the gas outlet.2. The apparatus of claim 1 wherein the variable aperture comprises aflexible seal.
 3. The apparatus of claim 2 wherein the variable apertureis configured for proportional opening over a range of flow values, therange of flow being between a first flow value and a second flow value.4. The apparatus of claim 3 wherein the first flow value isapproximately 0 lifers per minute and the second flow value isapproximately 70 liters per minute.
 5. The apparatus of claim 3 whereinthe variable aperture is configured for a fixed opening size for flowvalues above the range of flow.
 6. The apparatus of claim 5 wherein thevariable aperture is configured to be closed at the first flow value ofthe range of flow.
 7. The apparatus of claim 2 wherein the variableaperture further comprises a seal activation chamber.
 8. The apparatusof claim 7 wherein pressure of the seal activation chamber is set bycontrol of at least one electro-mechanical valve.
 9. The apparatus ofclaim 8 wherein the controller is configured to set the at least oneelectromechanical valve as a function of a measure of the level of flowof breathable gas.
 10. The apparatus of claim 1 wherein the aperturecomprises an electro-mechanical valve.
 11. The apparatus of claim 10wherein the controller is configured to set a size of an opening of theelectromechanical valve as a function of a measure of the level of flowof breathable gas.
 12. A respiratory treatment apparatus configured toprovide a supply of pressurized breathable gas to a patient insuccessive respiratory cycles, each cycle including an inspiration phaseand an expiration phase, said apparatus comprising: a gas inlet; a gasoutlet; and a flow generator adapted to receive an inlet flow ofbreathable gas from the gas inlet and to pressurize the breathable gasprior to delivery to the gas outlet; and a controller adapted to controlthe level of pressure generated by the flow generator to provide aninspiratory pressure and an expiratory pressure, wherein during at leasta portion of the expiration phase the inlet flow to the flow generatoris interrupted to facilitate a reduction in pressure from theinspiratory pressure to the expiratory pressure.
 13. The apparatus ofclaim 12 wherein the interruption of the inlet flow unloads a blower ofthe flow generator.
 14. The apparatus of claim 12 wherein the controlleris configured to interrupt-the inlet flow by setting one or moreelectro-mechanical valves.
 15. The apparatus of claim 14 furthercomprising a flexible seal in a flow path of the inlet and a sealactivation chamber proximate to the flexible seal, wherein the settingof the electro-mechanical valve controls a pressure level of the sealactivation chamber.
 16. A flow generator for a respiratory treatmentapparatus comprising: a motor; an impeller coupled with the motor; ahousing for the impeller comprising a volute, a gas inlet and a gasoutlet, the gas outlet being adaptable for a conduit of a patientinterface to deliver breathable gas as a respiratory treatment; an inletflow seal positioned to selectively open and close the gas inlet, theinlet flow seal having a first side internally proximate to an inletchamber of the gas inlet and the inlet flow seal having a second sideexternally proximate to the inlet chamber of the gas inlet; and a sealactivation chamber configured proximate to the second side of the inletflow seal to permit a negative pressure in the seal activation chamberto open the gas inlet to a flow of breathable gas.
 17. The flowgenerator of claim 16 wherein the housing further comprises first andsecond ports and a pressure communication conduit to connect the inletchamber and the seal activation chamber for pressure communication suchthat a change in pressure in the inlet chamber changes the pressure inthe seal activation chamber.
 18. The flow generator of claim 17 furthercomprising a first flow control valve coupled with the pressurecommunication conduit, wherein the first flow control valve isconfigured to selectively open and close the seal activation chamber toatmospheric pressure.
 19. The flow generator of claim 18 wherein thechange in pressure is a decrease associated with a patient induced flowof breathable gas from the gas inlet to the gas outlet.
 20. The flowgenerator of claim 19 wherein the decrease in pressure in the sealactivation chamber is discontinued when the first flow control valve isset to open the seal activation chamber to atmospheric pressure andwherein the discontinued decrease in pressure permits closure of the gasinlet to a flow of breathable gas.
 21. The flow generator of claim 18wherein, when the first flow control valve is set to permit equalizationbetween the seal activation chamber and the gas inlet chamber, a backflow from the gas outlet to the gas inlet increases pressure in theinlet chamber and the seal activation chamber such that the increase inpressure permits closure of the gas inlet and whereby the back flow isstopped.
 22. The flow generator of claim 18 wherein the inlet flow sealcomprises a flexible membrane.
 23. The flow generator of claim 22wherein the gas inlet comprises an aperture that is sealable by theinlet flow seal and wherein a surface area of the inlet flow seal isgreater than an aperture area, of the aperture.
 24. The flow generatorof claim 18 further comprising a second flow control valve coupled withthe first flow control valve, wherein the second flow control valve isconfigured to selectively open and close the gas inlet to pressure ofthe gas outlet.
 25. The flow generator of claim 24 wherein the first andsecond flow control valves are configured to selectively seal a pressurelevel within the seal activation chamber such that the seal activationchamber discontinues equalizing with a pressure of the gas Inlet chamberand an ambient pressure.
 26. The flow generator of claim 25 wherein thesecond flow control valve is configured to selectively open and closethe first flow control valve to equalize with ambient pressure of thegas inlet and the first flow control valve is configured to selectivelyopen and close the seal activation chamber to the first flow controlvalve.
 27. The flow generator of claim 25 further comprising: acontroller configured to set the first flow control valve in response toa detection of a condition of inspiration to permit equalization ofpressure in the seal activation chamber with pressure of the gas inletchamber so as to permit an inspiratory flow to open the gas inlet. 28.The flow generator of claim 27 wherein the controller is configured toset the first flow control valve in response to a detection of acondition of expiration to discontinue the decrease in pressure in theseal activation chamber to close the gas inlet to a flow of breathablegas.
 29. The flow generator of claim 28 further comprising a controllerconfigured to set the first flow control valve and the second flowcontrol valve in response to a detection of a condition of inspirationto seal a pressure in the seal activation chamber and to lock open thegas inlet to permit a back flow of breathable gas.
 30. The flowgenerator of claim 18 further comprising an oxygen input port coupled tothe inlet to allow injection of oxygen gas into the inlet.
 31. The flowgenerator of claim 16 further comprising an oxygen input port coupled tothe gas outlet to allow injection of oxygen gas into the flow ofbreathable gas.
 32. A respiratory treatment apparatus comprising: a flowgenerator to produce a breathable gas at a pressure above atmosphericpressure for a pressure therapy regime, the flow generator comprising agas inlet and a gas outlet, the gas outlet being adaptable for a conduitof a patient interface to deliver the breathable gas; a controller tocontrol the flow generator to produce the breathable gas according to apressure therapy regime; an inlet flow seal positioned to selectivelyopen and close the gas inlet, the inlet flow seal having a first sideinternally proximate to an inlet chamber of the gas inlet and the inletflow seal having a second side externally proximate to the inlet chamberof the gas inlet; and a seal activation chamber proximate to the secondside of the inlet flow seal wherein a negative pressure in the sealactivation chamber permits opening of the gas inlet with a flow ofbreathable gas.
 33. The apparatus of claim 32 further comprising apressure communication conduit to connect the inlet chamber and the sealactivation chamber for pressure communication such that a change inpressure in the inlet chamber changes the pressure in the sealactivation chamber.
 34. The apparatus of claim 33 further comprising afirst flew control valve being coupled with the pressure communicationconduit and being configured to selectively open and close the sealactivation, chamber to atmospheric pressure under control of thecontroller.
 35. The apparatus of claim 34 wherein the flow generatorcomprises a motor, volute and an impeller configured between the gasinlet and the gas outlet.
 36. The apparatus of claim 35 wherein thenegative pressure in the seal activation chamber is discontinued whenthe first flow control valve is set to open the seal activation chamberto atmospheric pressure and wherein the discontinued negative pressurepermits closure of the gas inlet to a flow of breathable gas.
 37. Theapparatus of claim 33 wherein, when the first flow control valve is setto permit equalization between the seal activation chamber and the gasinlet chamber, a back flow from the gas outlet to the gas inletincreases pressure in the inlet chamber and the seal activation chambersuch that the increase in pressure permits closure of the gas inlet andwhereby the back flow is stopped.
 38. The apparatus of claim 36 whereinthe inlet flow seal comprises a flexible membrane.
 39. The apparatus ofclaim 38 wherein the gas inlet comprises an aperture that is scalable bythe inlet flow seal and wherein a surface area of the inlet flow seal isgreater than an aperture area of the aperture.
 40. The apparatus ofclaim 34 further comprising a second flow control valve being coupledwith the first flow control valve and being configured to selectivelyopen and close the gas inlet to pressure of the gas outlet.
 41. Theapparatus of claim 40 wherein the first and second control valves, areconfigured to selectively seal a pressure level within the sealactivation chamber such that the seal activation chamber discontinuesequalizing with a pressure of the gas inlet chamber and an ambientpressure and wherein the sealed pressure level locks the inlet flow sealin an open position.
 42. The apparatus of claim 41 wherein the secondflow control valve is configured to selectively open and close the firstflow control valve to equalize with ambient pressure of the gas inletand the first flow control valve is configured to selectively open andclose the seal activation chamber to the first flow control valve. 43.The apparatus of claim 34 wherein the controller is further configuredto set the first flow control valve in response to a detection of acondition of inspiration to permit the decrease in pressure in the sealactivation chamber to open the gas inlet to a flow of breathable gas.44. The apparatus of claim 43 wherein the controller is configured toset the first flow control valve in response to a detection of acondition of expiration to discontinue the decrease in pressure in theseal activation chamber to close the gas inlet to a flow of breathablegas.
 45. The apparatus of claim 32 further comprising an oxygen inputport coupled to the inlet to allow injection of oxygen gas into theinlet.
 46. The apparatus of claim 32 further comprising an oxygen inputport coupled to the gas outlet to allow injection of oxygen gas into theflow of breathable gas.
 47. A system for regulating flow to a flowgenerator in a respiratory treatment apparatus, the system comprising: agas inlet, to a flow generator through which a flow breathable gas isinspired, means for sealing off the flow at the gas inlet, the means forsealing comprising a first side internally proximate to an inlet chamberof the gas inlet and a second side externally proximate to the inletchamber of the gas inlet; chamber means proximate to the second side ofthe means for sealing wherein a negative, pressure therein permitsopening of the gas inlet at the means for sealing; means for changingpressure to the chamber means in accordance with a change in pressure inthe gas inlet; and means for selectively discontinuing the change inpressure in the chamber means while permitting the change in pressure inthe gas inlet.
 48. The system of claim 47 further comprising an oxygeninput port coupled to the inlet to allow injection of oxygen gas intothe gas inlet.
 49. The system of claim 47 further comprising an oxygeninput port coupled to the gas outlet to allow injection of oxygen gasinto the flow of breathable gas.
 50. The system of claim 47 wherein aback flow is prevented in accordance with an equalized pressurecondition between the chamber means and the gas inlet at the first side.51. The system of claim 47 wherein a forward flow is prevented inaccordance with an equalized pressure condition between the chambermeans and ambient pressure.
 52. The system of claim 47 wherein a backflow is permitted in accordance with a sealed pressure condition of thechamber means that locks open the means for sealing off the flow.